I am trying to calibrate and profile my display for a color-managed workflow in photography.
I have installed colord-kde and the argyll -toolset for monitor calibration. I wanted first to calibrate my display and did run
dispcal -v -o -t 6500 -g 2,1 Dell_2209WA
,and then to install the LUT calibration data with
dispwin -I Dell_2209WA.icc
I can see my calibration file installed in ~/user/.config/color/icc/devices/display/Dell_2209WA.icc
The monitor is not profiled yet. I want to ensure the calibration works before profiling.

How can I know/ensure that the calibration LUT will be loaded at every boot by KDE / Plasma ?

When I go to the SystemSettings/Color Corrections/Devices/Dell-display it still shows: Display corrections – None, White Point D50 and there is some (Default) Profile loaded. That does not match with the information I have in the monitor calibration. Is there some default profile installed by colord/Plasma ?

Another peculiarity is the Note on the Color Corrections -settings page: ”You need Gnome Color Management installed in order to calibrate devices”. Also, the "Calibration" button is greyed out. But I seem to have the gnome-color-manager installed ! Do I need to install something additional to manage colors in KDE Plasma ?

I am using KDE neon 5.20 with

KDE Plasma Version: 5.20.4
KDE Frameworks Version: 5.77.0
Qt Version: 5.15.2
Kernel Version: 5.4.0-58-generic
OS Type: 64-bit
Processors: 12 × AMD Ryzen 5 2600 Six-Core Processor
Memory: 15,6 GiB of RAM
Graphics Processor: Radeon RX 580 Series

Update Jan 3rd,2021
I have been playing around, trying to understand and to get color management working. I have now prfiled my display also. This is my experience and findings so far:
There is little information and instruction on color management in KDE Plasma. Distros and desktop environments are different and it is not clear what applies and what does not. It appears to me that KDE Plasma / colord is not well integrated with Argyll. If I understand it correctly, they use different (hopefully complementary) ways of communicating the systems profile information for the applications.

I need to load the calibration data (video card LUT) for each session at every start (dispwin -L seems to the job). I am still unclear where I should place the appropriate script. .xinitrc has been suggested in some posts but I am not 100% sure how that works in Plasma - or if there should be a better place for it.

Installing the profile with dispwin -I Profile.icc does not add it to the list of profiles SystemSettings/Color Corrections identify. Copying it to /usr/share/color/icc seems to do the job. After copying the profile to the correct location I was able to add it to the display in System Settings.

Few applications that I have tested seem to load it correctly. Digikam as an example.

I wish some knowledgeable people would comment and document the color management in Plasma better. For me, the remaining open question is: how to load the LUT properly ?